For safety reasons, circuit breakers are often used between an electrical appliance and the mains power source. In one typical construction, the circuit breaker has at least one pair of internal contacts for switching the electrical connection between the load and the power source, and includes an actuator for moving one of the contacts into contact with the other contact. A solenoid is operable to hold the two contacts together. An electronic control circuit is further included to detect the occurrence of a circuit fault and, in response to a fault, to disable the operation of the solenoid, thereby allowing the two contacts to separate.
The invention seeks to provide a circuit breaker of this type in general, having a novel construction.
According to a first aspect of the invention, there is provided a circuit breaker for use between a load and a power source, comprising a casing, at least two movable contacts inside the casing for electrical connection to said load and power source respectively, a movable contact holder holding a first of said at least two contacts, first resilient means biassing the contact holder to move, and an actuator arranged to move a second of said at least two contacts into contact with the first contact. A locking member is arranged to lock the contact holder and in turn the first contact at a specific position into the path of movement of the second contact, against the action of the first resilient means, for contact by the second contact. The locking member is supported for movement between a first position locking the contact holder in said specific position and a second position releasing the contact holder from said specific position. Second resilient means biasses the locking member towards the second position. An electromagnetic device is operable to hold the locking member in the first position against the action of the second resilient means. An electronic control circuit is adapted to detect the occurrence of a circuit fault and in response to disable the operation of the electromagnetic device.
Preferably, the first and second resilient means comprise separate springs.
In a preferred embodiment, the circuit breaker includes third resilient means biassing the actuator to move the second contact into contact with the first contact.
More preferably, the actuator has a part engaging the contact holder in one direction to limit the movement of the contact holder by the first resilient means in the opposite direction and to move the contact holder simultaneously in said one direction in a spaced apart relationship against the action of both the first and the third resiliently means.
It is preferred that the first contact is carried by the contact holder for movement thereby.
It is preferred that the second contact is carried by the actuator for movement thereby.
Preferably, the contact holder and the actuator are moveable along substantially parallel axes, and the electromagnetic device has a central axis that is substantially parallel to the axes of the contact holder and the actuator.
Preferably, the electromagnetic device comprises a solenoid and a ferromagnetic core and is operable to hold the locking member in the first position by way of magnetic attraction.
In a specific construction, the locking member is supported for pivotal movement, and comprises a first planar member adjacent the contact holder and a second planar member adjacent the electromagnetic device, said two planar members being connected substantially perpendicularly together.
More specifically, the contact holder includes a protrusion on one side, and the first planar member includes a detent on the same side for engaging the protrusion and thus detaining the contact holder at said specific position.
More specifically, the second planar member has a free end supporting a member which is susceptible to magnetic attraction by the electromagnetic device.
In a preferred embodiment, the circuit breaker includes two said first contacts and two said second contacts, wherein each pair of one first contact and one second contact is provided on a respective left/right side of the casing, said one first contact and one second contact being for electrical connection in a respective live/neutral circuit to said load and power source respectively.
The casing may be in the form of a power plug having power pins for insertion into a socket of said power source and including a rear opening to permit the entrance of a power cord connected to said load.
According to a second aspect of the invention, there is provided a circuit breaker for use between a load and a power source, comprising a casing, at least two movable contacts inside the casing for electrical connection to said load and power source respectively, and a movable contact holder holding a first of said at least two contacts. A resiliently biassed actuator is arranged to move against the action of resilience both said at least two contacts in a spaced part relationship in one direction and subsequently to move under the action of resilience a second of said at least two contacts in the opposite direction into contact with the first contact. A movable locking member is arranged to stop movement of the first contact in said opposite direction for contact by the second contact. An electromagnetic device is operable to hold the locking member in a position stopping movement of the first contact in said opposite direction. An electronic control circuit is adapted to detect the occurrence of a circuit fault and in response to disable the operation of the electromagnetic device.